GPS-2R (Global Positioning System) or Navstar-2RM (Navigation System using Timing And Ranging) are the third evolution stage of the second generation of the GPS satellites.

The GPS-IIR replenishment satellites are produced by General Electric Astrospace (later Martin Marietta and Lockheed Missiles & Space) under a contract issued in 1989, which included 21 satellites based on the commercial AS-4000 bus. These provided improved navigation accuracy and longer autonomous satellite operation than earlier model GPS satellites. The satellites were three-axis stabilized and operated at downlink frequencies of 1572.42 MHz and 1227.6 MHz (L-Band) and 2227.5 MHz (S-Band). Lockheed was responsible for launch and flight operations support of the GPS-IIR through 2006.

Block IIR satellites provided dramatic improvements over previous blocks. They could determine their own position by performing inter-satellite ranging with other IIR vehicles. They also had reprogramable satellite processors enabling problem fixes and upgrades in flight, increased satellite autonomy, and radiation hardness.